The present invention relates to composite materials for cooking apparatuses which are produced by applying, to a substrate, a fluorine-containing polymer excellent in heat resistance, non-sticking property, transparency (property for exhibiting clear surface pattern), stain-proofing property and water- and oil-repelling property and particularly in adhesive property to the substrate.
With respect to cooking apparatuses represented by a griddle and a rice cooker, it is desired that cooking can be done at higher temperature for shortening of cooking time and to pursue good taste of cooked dishes. Also it is desired that stains such as oil and scorch can be easily removed so as to make cleaning of these apparatuses easy after the cooking. Further good property for exhibiting clear surface pattern is also desired from the viewpoint of appearance thereof.
In order to meet such requirements, for the composite materials used for cooking apparatuses (cooking appliances, wares, utensils, tools, etc.), a fluorine-containing resin which is excellent in heat resistance, chemical resistance, weather resistance, surface properties (friction resistance, etc.), electric insulating property and the like is used in the form of coating or film.
However the fluorine-containing resin involves a substantial problem, namely insufficient adhesion to a metal or glass substrate due to its excellent non-sticking property.
Therefore in case where the fluorine-containing resin is used in the form of coating, there is a method of adhering a fluorine-containing resin to a substrate by roughening the surface of metal chemically or physically with expecting anchor effect between them. However this method requires much labor in the surface roughening itself, and though initial adhesion is possible, lowering of the anchor effect arises when a temperature change is made repeatedly and in case of use at high temperature.
Also a method for chemically activating a surface of a fluorine-containing resin by treating the surface with a solution prepared by dissolving metallic sodium in liquid ammonia has been proposed. However in that method, not only there is a fear that the solution itself causes environmental pollution but also there is a problem that its handling is attended with danger.
Further though a method for carrying out physical and chemical treatment such as plasma sputtering on a surface of a fluorine-containing resin has been proposed, there is a problem that much labor is required for the treatment and an increase in cost is resulted.
Also in order to improve adhesion of a fluorine-containing resin coating composition, investigations with respect to addition of various components and use of a primer have been made.
For example, there is a technique of adding an inorganic acid such as chromic acid to a coating composition containing a fluorine-containing resin to form chemical conversion coating film on a surface of metal for enhancing adhesion of the composition (JP-B-63-2675). However since chromic acid contains hexahydric chromium, it cannot be said that such a technique is sufficient in view of safety in food and coating work. Further in case of use of other inorganic acids such as phosphoric acid, there was a problem that safety of a fluorine-containing resin coating composition is damaged.
Use of a coating composition containing a fluorine-containing resin as a primer, in which heat resistant resins such as polyamideimide, polyimide, polyethersulfone and polyether ether ketone and in addition, a metal powder are added instead of the above-mentioned inorganic acid, has been studied (JP-A-6-264000). Inherently there is almost no compatibility between a fluorine-containing resin and a heat resistant resin. Therefore there arises a phase separation in a coating film, thus easily causing intercoat adhesion failure between the primer and the top coat of the fluorine-containing resin. Further film defects such as pin holes and cracks arise easily at the time of processing at high temperature or during use due to a difference in heat shrinkage between the fluorine-containing resin and the heat resistant resin or due to lowering of elongation of the coating film by the addition of the heat resistant resin. Also since those heat resistant resins are colored brown by baking, property for exhibiting clear surface pattern is poor and it is difficult to use them for applications requiring white and vivid colors and transparency. Further when the heat resistant resin is blended, non-sticking property and friction resistance which the fluorine-containing resin possesses inherently are lowered.
Also for adhesion of a fluorine-containing resin coating composition to glass, etc. requiring transparency, an improvement of the adhesion has been tried by treating the substrate with a silane coupling agent or adding a silicone resin to the fluorine-containing resin coating composition (JP-B-54-42366, JP-A-5-177768). However enhancement of adhesion is insufficient, heat resistance is lowered and separation of film, foaming and coloring arise easily at sintering or in use at high temperature.
On the contrary, fluorine-containing resin coating compositions prepared by copolymerizing a hydrocarbon monomer (containing no fluorine) containing functional group such as hydroxyl or carboxyl have been discussed. However those coating compositions were originally studied mainly for a purpose of weather resistance, and it is difficult to use them for application requiring heat resistance at 200xc2x0 to 350xc2x0 C. which is directed by the present invention, and for applications requiring non-sticking property, friction resistance, etc.
Namely with respect to a polymer prepared by copolymerizing a hydrocarbon monomer (containing no fluorine) having functional group, thermal decomposition easily occurs on components of the monomer at the time of processing at high temperature or during use, and thus coating film failure, coloring, foaming, separation, etc. arise, which makes it impossible to attain purposes of coating a fluorine-containing resin.
Further fluorine-containing resins are generally insufficient in mechanical strength and dimensional stability, and high in price. In order to make the best use of the above-mentioned merits of the fluorine-containing polymer and minimize its disadvantages, investigations have been made also with respect to its use in the form of film.
However the fluorine-containing resin inherently has low adhesive force, and it is difficult to adhere the fluorine-containing resin directly to other material (substrate). For example, even if the adhering is tried by thermo-processing, adhesive strength of the fluorine-containing resin is not enough, or even if the resin has adhesive force to a certain extent, such an adhesive force is apt to vary depending on kind of the substrate. Thus in many cases, reliability on the adhesive strength of the fluorine-containing resin has been not so enough.
In order to adhere the fluorine-containing resin film to a substrate, mainly the following methods have been studied:
1. a method for physically roughening a surface of substrate by sand blasting, etc.,
2. a method for surface-treating a fluorine-containing resin film by chemical treatment such as sodium etching, plasma treatment, photochemical treatment, etc.,
3. a method for adhering by using an adhesive, and other methods. With respect to the methods 1 and 2 above, surface-treating steps are required, and the steps are complicated and productivity is poor. Also kinds and shapes of substrates are restricted. The fluorine-containing resin film inherently has low adhesive force, and there easily occur problems with appearance such as coloring and color (property for exhibiting clear surface pattern) of the obtained composite material. Also the method of using a chemical such as sodium etching has a problem with safety.
Use of an adhesive in the method 3 above has also been discussed. A usual hydrocarbon type (non-fluorine-containing) adhesive does not have enough adhesive property and its heat resistance is insufficient. Thus a hydrocarbon type adhesive cannot stand under conditions for adhering of a fluorine-containing polymer film, which requires molding and processing at high temperature, and peeling due to decomposition of the adhesive and coloring occur. The above-mentioned laminated article produced by using an adhesive also lacks in reliability with respect to its adhesive property, since an adhesive layer is insufficient in heat resistance, chemical resistance and water resistance and its adhesive force cannot be maintained due to a change in temperature and environment.
On the contrary, adhesion by using an adhesive and adhesive composition comprising a fluorine-containing polymer having functional group is discussed.
For example, it is reported that a fluorine-containing polymer prepared by graft-polymerizing, to the fluorine-containing polymer, a hydrocarbon monomer which has carboxyl represented by maleic anhydride and vinyltrimethoxysilane, a residual group of carbonic acid, epoxy or a hydrolyzable silyl group, is used as an adhesive (for example, JP-A-7-18035, JP-A-7-25952, JP-A-7-25954, JP-A-7-173230, JP-A-7-173446, JP-A-7-173447) and that an adhesive composition comprising a fluorine-containing copolymer prepared by copolymerizing a hydrocarbon monomer having functional group such as hydroxyalkyl vinyl ether with tetrafluoroethylene or chlorotrifluoroethylene and an isocyanate hardening agent is cured and used as an adhesive between vinyl chloride and corona-discharged ETFE (for example, JP-A-7-228848).
The above-mentioned adhesive or adhesive composition comprising a fluorine-containing resin prepared by graft-polymerizing or copolymerizing a hydrocarbon monomer having functional group does not have enough heat resistance, and thus at the time of processing a composite material comprising the adhesive or adhesive composition and a fluorine-containing resin film at high temperature or during use at high temperature, decomposition and foaming occur, thereby causing reduction of adhesive strength, peeling and coloring. In case of the adhesive composition disclosed in JP-A-7-228848, it is necessary to corona-discharge the fluorine-containing resin film.
As mentioned above, there have been no material for composite materials for cooking apparatuses which meets the above-mentioned requirements and assures strong adhesion to a substrate and excellent property for exhibiting clear surface pattern.
In view of the above-mentioned facts, an object of the present invention is to provide composite materials for cooking apparatuses which are produced by applying, to a substrate, a material comprising a fluorine-containing polymer being excellent in adhesion to the substrate without necessitating complicated steps.
Further an object of the present invention is to provide composite materials for cooking apparatuses which are excellent in non-sticking property, stain-proofing property, water- and oil-repelling property, stain removing property, chemical resistance, rust preventing property, antibacterial property, resistance to energy ray and friction resistance.
The present invention relates to composite materials for cooking apparatuses which are produced by applying, to a substrate, a material comprising a fluorine-containing ethylenic polymer having functional group and prepared by copolymerizing:
(a) 0.05 to 30% by mole of at least one of fluorine-containing ethylenic monomers having at least one functional group selected from the group consisting of hydroxyl, carboxyl, a carboxylic salt group, a carboxylic ester group and epoxy and
(b) 70 to 99.95% by mole of at least one of fluorine-containing ethylenic monomers having no functional group mentioned above.
In that case, it is preferable that the above-mentioned fluorine-containing ethylenic monomer (a) having functional group is at least one of fluorine-containing ethylenic monomers represented by the formula (1):
CX2xe2x95x90CX1xe2x80x94Rfxe2x80x94Yxe2x80x83xe2x80x83(1)
wherein Y is xe2x80x94CH2OH, xe2x80x94COOH, a carboxylic salt group, a carboxylic ester group or epoxy, X and X1 are the same or different and each is hydrogen atom or fluorine atom, Rf is a divalent alkylene group having 1 to 40 carbon atoms, a fluorine-containing oxyalkylene group having 1 to 40 carbon atoms, a fluorine-containing alkylene group having ether bond and 1 to 40 carbon atoms or a fluorine-containing oxyalkylene group having ether bond and 1 to 40 carbon atoms.
Further it is preferable that the above-mentioned fluorine-containing ethylenic monomer (b) having no functional group is tetrafluoroethylene.
Further it is preferable that the above-mentioned fluorine-containing ethylenic monomer (b) having no functional group is a monomer mixture of 85 to 99.7% by mole of tetrafluoroethylene and 0.3 to 15% by mole of a monomer represented by the formula (2):
CF2xe2x95x90CFxe2x80x94Rf1xe2x80x83xe2x80x83(2)
wherein Rf1 is CF3 or ORf2, in which Rf2 is a perfluoroalkyl group having 1 to 5 carbon atoms.
Further it is preferable that the above-mentioned fluorine-containing ethylenic monomer (b) having no functional group is a monomer mixture comprising 40 to 80% by mole of tetrafluoroethylene, 20 to 60% by mole of ethylene and 0 to 15% by mole of other monomer copolymerizable with those monomers.
Also the present invention relates to the composite materials for cooking apparatuses, which are produced by applying, to a substrate, the above-mentioned fluorine-containing ethylenic polymer having functional group in the form of coating.
Also the present invention relates to the composite materials for cooking apparatuses, which are produced by applying, to a substrate, the above-mentioned fluorine-containing ethylenic polymer having functional group in the form of an aqueous dispersion.
Also the present invention relates to the composite materials for cooking apparatuses, which are produced by applying, to a substrate, the above-mentioned fluorine-containing ethylenic polymer having functional group in the form of a powder coating composition.
Also the present invention relates to the composite materials for cooking apparatuses, which are produced by applying, to a substrate, the above-mentioned fluorine-containing ethylenic polymer having functional group in the form of a film.
It is preferable that the above-mentioned substrate is a metallic substrate.
Also it is preferable that the above-mentioned substrate is a glass substrate.
The present invention relates to cooking apparatuses produced by using the composite materials for cooking apparatuses.
Also the present invention relates to heating apparatuses for cooking produced by using the composite materials for cooking apparatuses.
Also the present invention relates to a griddle produced by using the composite materials for cooking apparatuses.
Also the present invention relates to a griddle produced by using the composite materials for cooking apparatuses on its heating surface made of metal.
Also the present invention relates to a griddle produced by using the composite materials for cooking apparatuses on its glass lid.
Also the present invention relates to a range with oven produced by using the composite materials for cooking apparatuses.
Also the present invention relates to a range with oven produced by using the composite materials for cooking apparatuses on its inner surface made of metal.
Also the present invention relates to a range with oven produced by using the composite materials for cooking apparatuses on its cooking plate.
Also the present invention relates to a range with oven produced by using the composite materials for cooking apparatuses on its glass door.
Also the present invention relates to a heating pot produced by using the composite materials for cooking apparatuses.
Also the present invention relates to a heating pot produced by using the composite materials for cooking apparatuses on its heating surface made of metal.
Also the present invention relates to a heating pot produced by using the composite materials for cooking apparatuses on its glass lid.
Also the present invention relates to a frying pan produced by using the composite materials for cooking apparatuses.
Also the present invention relates to a frying pan produced by using the composite materials for cooking apparatuses on its heating surface made of metal.
Also the present invention relates to a fryer produced by using the composite materials for cooking apparatuses.
Also the present invention relates to a fryer produced by using the composite materials for cooking apparatuses on its inner surface made of metal.
Also the present invention relates to a fryer produced by using the composite materials for cooking apparatuses on its inner surface made of glass.
Also the present invention relates to a rice cooker produced by using the composite materials for cooking apparatuses.
Also the present invention relates to a rice cooker produced by using the composite materials for cooking apparatuses on its inner surface made of metal.
Also the present invention relates to a rice cooker produced by using the composite materials for cooking apparatuses on its inner lid made of metal.
Also the present invention relates to a pot produced by using the composite materials for cooking apparatuses.
Also the present invention relates to a pot produced by using the composite materials for cooking apparatuses on its inner surface made of metal.
Also the present invention relates to a pot produced by using the composite materials for cooking apparatuses on its inner lid made of metal.
Also the present invention relates to a tableware or vessel produced by using the composite materials for cooking apparatuses.
Also the present invention relates to a metallic tableware or vessel produced by using the composite materials for cooking apparatuses.
Also the present invention relates to a glass tableware or vessel produced by using the composite materials for cooking apparatuses.
Also the present invention relates to cooking apparatuses for processing foods which are produced by using the composite materials for cooking apparatuses.
Also the present invention relates to cooking apparatuses for mixing foods which are produced by using the composite materials for cooking apparatuses.
Also the present invention relates to cooking apparatuses for cutting foods which are produced by using the composite materials for cooking apparatuses.
Also the present invention relates to baking apparatuses produced by using the composite materials for cooking apparatuses.